Abstract
The endophytic mutualism of plants with microorganisms often leads to several benefits to its host including plant health and survival under extreme environments. Arnebia euchroma is an endangered medicinal plant that grows naturally in extreme cold and arid environments in the Himalayas. The present study was conducted to decipher the cultivable endophytic diversity associated with the leaf and root tissues of A. euchroma. A total of 60 bacteria and 33 fungi including nine yeasts were isolated and characterized at the molecular level. Among these, Proteobacteria was the most abundant bacterial phylum with the abundance of Gammaproteobacteria (76.67%) and genus Pseudomonas. Ascomycota was the most abundant phylum (72.73%) dominated by class Eurotiales (42.42%) and genus Penicillium among isolated fungal endophytes. Leaf tissues showed a higher richness (Schao1) of both bacterial and fungal communities as compared to root tissues. The abilities of endophytes to display plant growth promotion (PGP) through phosphorus (P) and potassium (K) solubilization and production of ACC deaminase (ACCD), indole acetic acid (IAA), and siderophores were also investigated under in vitro conditions. Of all the endophytes, 21.51% produced ACCD, 89.25% solubilized P, 43.01% solubilized K, 68.82% produced IAA, and 76.34% produced siderophores. Six bacteria and one fungal endophyte displayed all the five PGP traits. The study demonstrated that A. euchroma is a promising source of beneficial endophytes with multiple growth-promoting traits. These endophytes can be used for improving stress tolerance in plants under nutrient-deficient and cold/arid conditions.
Highlights
Plants are believed to coevolve with their microbial symbionts which are the integral components of a plant’s life cycle (Compant et al, 2019)
All the bacterial endophytes were identified to species level with more than 99% similarity using the EzTaxon/NCBI database except ALB20, ARB6, and ARB37, which were identified to genus level as Pseudomonas spp. (Supplementary Table 1)
Among 60 bacterial endophytes, 83.34% bacterial endophytes belonged to class Proteobacteria, which were further classified into Gammaproteobacteria (76.67%), Alphaproteobacteria (5%), and Betaproteobacteria (1.67%)
Summary
Plants are believed to coevolve with their microbial symbionts which are the integral components of a plant’s life cycle (Compant et al, 2019). Endophytic mutualism, involving an endophyte that colonizes internal tissues of a plant without causing any apparent symptoms to its host, is of special interest because endophytes spend all or part of their life cycle. Beneficial Endophytes of Arnebia euchroma inside the plant tissues and directly influence host cells. The mutualism between endophytes and its host plant species is sustained through the production or induction of metabolites required for the growth or protection of plants against adverse environmental conditions or pathogens (Li F. et al, 2020). The role of endophytes in the primary and secondary metabolism of host plants and as a source of important secondary metabolites is demonstrated in various plant species (Pandey et al, 2016, 2018)
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